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Discussion Starter #1
i just puta speedwerx pipe on my 07 500 and changed thejet from the factory 40 to a 48 which was supplied. now when i let off the throttle it has a real nasty backfire, what would be causing this?
 

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the main jet. get a dyno jet kit.
 

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x2, or get a bigger main jet. 1 to 2 steps up should do it. You probably need to richen the top end also. The jet you put in is a low rpm jet. The main feeds the top end, which may be lean also.
 

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If all you did was add the pipe its probably not that far off, but a lean condition can overheat a motor depending on what you do. Hard riding wide open is not good.
 

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i'm gonna disagree with crasher a little here. the pipe leans out the top quite a bit IMO. you could just buy a handful of mains but good luck getting the needle right. the needle controls 1/4 to 3/4 throttle where most riding is done. get the dj kit.

also read jetting 101 in pinned topics.
 

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Does the JD kit have different needle settings too? Thats some fine tuning.
I guess reflecting on my own muffler mods, I did end up jetting pretty close to sea level, and IM at 8500 ft.
 

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ya the dj needle has 6 clips vs none. and about half as thick.
 

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The backfire on decel is a lean condition in the partial or lower throttle settings.

Did you drill the slide on the carb ? This helps this situation.

The Dyno Jet jet kit is a great kit for that machine as well. The adjustable needle will help allow you to be able to tune away from this issue.

You do not want the machine to be backfiring, this can and will cause the silencer to fail.
 

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Discussion Starter #10
i drilled the slide before, will by adding the dyno jet kit give it abit more power? thanks for all your replies!
 

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it might add power, important part is it'll stop meltdown.
 

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Two things about the DJ kit. You'll gain power because the needle taper is better on the DJ needle. Secondly, when I put the SW pipe on my H1 they (Speedwerx) told me that the large pilot that was supplied could be reduced down if I was using a DJ needle (which I was). I went from a 48 (I believe that's what they sent with the pipe) and now I run a 42...and it's spot on.
 

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That just shows how bad the stock needle is after you install a pipe or a snorkel because they have to raise the pilot size to help the jeting curcit because the needle does not supply the needed fuel.

that needle is worth the money as far as making the bike run right
 

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Discussion Starter #15
ok, so i finally got my dj kit and im 1800ft above sea level, where would be best to start with my needle and jetting. i run from -25c to +30c. thanks
 

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I would stick the needle on the 4th knotch. along with the pilot they sent you (with your pipe) and maybe a 142 main jet and se how that does. If you had a 2" snorkel i would say the 146-150dj mian would be best but without iam going to guess a good place to start would be the 142.
 

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I run a DJ 144 main with a #42 pilot three turns out. Runs decent but I think it needs a #45. I don't get backfire, but still get a little grumbling (best I can describe it) on deceleration. I have a drilled out stock exhaust and 2" snorkel.
 

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yeah i bet the 45 pilot would fix it for you. my 500 never was happy with the 42 pilot once i snorkeled and installed a good muffler.
 

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Discussion Starter #19
ok, so i read the instructions and added a 146dj and put the needle on the 3rd clip, it runs great! it seems to be a little sluggish on the top, what should my next move be? on a good note it does not backfire anymore
 

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With no snorkel i would step the main jet down in size, go down to the next size in the kit and see how it feels it sounds like it might be a touch on the rich side to me.
 
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